Circuit breakers are well known in the art, and are designed to trip in response to an electrical interruption event caused by an overload, short circuit, or thermal runaway condition, thereby opening the circuit to which the circuit breaker is connected and reducing the possibility of damage to the conductor wires or the loads connected to the circuit breaker. A circuit breaker can be reset (either manually or automatically) to resume power flow to the loads.
Typically, power conductors are connected to a circuit breaker through mechanical pressure via, e.g., screw-type or compression lugs. Although the circuit breakers themselves normally provide reliable protection for many years, the mechanical connections holding the power conductors can loosen, resulting in higher circuit impedance, higher temperatures, and possibly damage to insulation or even fire hazards. Preventive maintenance techniques include manual inspection testing with infrared sensing equipment for diagnosing loose connections and/or defective bus joints before problems occur in electrical distribution equipment (e.g., switchgear, panelboards, motor control centers, etc.). Such testing involves the expense of the service itself and, additionally, has the disadvantage that, due to its periodic nature, some potential problems may not be detected in a timely fashion.
What is needed, therefore, is a circuit breaker having a device for sensing the temperature of the circuit breaker's power conductors.